Open and closed circulatory systems Year 11: Biology http://intranet.cbhslewisham.nsw.edu.au:82/science/concepta.asp?conID=13&resource=1 Retrieved 4 June 2011

Outcome: compare the open and closed circulatory systems using one vertebrate and one invertebrate

The circulatory systems of invertebrates Invertebrates such as insects have a heart The heart of a young snail, which has a thin shell, can sometimes be seen by holding the snail up to the light and looking up from below

Insects circulatory

Invertebrates have an open circulatory system Vertebrates have a closed circulatory system

The blood in a closed circulatory system remains within the tubes and materials diffuse in and out of the blood through the walls of tiny tubes called capillaries.

The circulatory systems in invertebrates is an open system Invertebrates blood is pumped at low pressure directly into the main body cavity where it slowly flows about the cells

The blood is collected by open vessels like drains, which carry the blood back to the heart like drains This inefficient circulatory system limits the size of invertebrates

Large vertebrates require a more efficient system to overcome their low surface area to volume ratio In insects, the open circulatory system is supplemented with another separate open system of gas exchange

Insects have a series of small holes (spiracles), which open into a network of tubes called tracheae. These tracheae distribute oxygen to body cells and carry away oxygen

This network relies on diffusion to move gases through them Unlike vertebrates, which transport wastes, nutrients and gases in insects occurs through two systems

In vertebrates, nutrients, oxygen, CO2 and other wastes are transported by the circulatory system.

Questions 1. Name three animals that would have a closed circulatory system 2. Name three animals that would have an open circulatory system

3. Vertebrates can grow much larger than insects, explain why this is so in terms of their circulatory capacity